In order to achieve very high fuel utilization (such as around 99%) in a fuel cell power plant, it is necessary to reduce the amount of hydrogen exiting the fuel cell. However, attempts to reach perfect utilization result in fuel starvation, typically in a spotty fashion, at various locations within individual cells, and in various cells. Recycling fuel, from the fuel flow field exits back to the fuel flow field inlets, allows the overall fuel cell stack utilization to be greater than the utilization in the fuel cells. Recycling also tends to cause a more even distribution of the fuel, and mitigates the effects of inert gases, such as nitrogen which migrates from the anode through the porous membrane.
Recycling the fuel requires a recycle blower or compressor which must be powered by electricity generated by the fuel cell, which is referred to as parasitic power. Further, pure hydrogen is difficult to pump due to its low density, and the pump motor must be appropriately rated to be non-sparking for safety.